Safety and Immunogenicity of a Prepandemic Influenza A (H5N1) Vaccine in Children

Background: The avian influenza A (H5N1) virus is considered to be a potential cause of the next influenza pandemic. Children may be particularly vulnerable to the pandemic virus, and they may react differently than adults to vaccines. We report the results of the first clinical trial of an H5N1 vaccine in children. Methods: Twelve healthy children (mean age +/- SD: 12.73 +/- 2.77 years) received a single dose of 6 mu g of the inactivated whole virus vaccine Fluval. Twenty-one days after vaccination, immunogenicity was assessed by hemagglutination inhibition and microneutralization assays. Safety information was collected for 180 days. Results: No side-effects were observed, and the vaccine fulfilled all applicable U.S. and European immunogenicity criteria for licensure. The post/prevaccination geometric mean titer ratio was 16.95, the rate of seroconversion was 75% and the rate of seroprotection was also 75% 21 days after vaccination. Conclusions: We confirmed our earlier findings of the present vaccine in adults showing encouraging safety and immunogenicity properties in children. Studies with the present vaccine in elderly subjects are underway.